The origins of the annual tradition actually date back hundreds of years to the pagan times when the celebration was all about marking the end of the harvest season.

Back then it was all about keeping the ghosts and ghouls away and it has only been recently that people have embraced the terror.

Here is everything you should know about the history of the day.

When is Halloween?

Halloween is marked on October 31 every year.

Why do we celebrate Halloween?

Aberystwyth University students in fancy dress (Picture: Alamy)

Halloween dates back to the pagan times and is thought to originate with the Celtic pagan festival of Samhain. Samhain was a celebration of the end of the harvest season, meaning ‘summer’s end’.

Gaels in this period are thought to have believed this time of year was also when the walls between the worlds were thin and porous and enabled spirits to pass through. Gaels feared the return of spirits through this thin wall between the worlds because they thought they might damage their crops for the next season.

As a result, to appease any spirits that would creep through, they would set up places at their dinner tables and offer the spirits food and drink. Bonfires would also be lit to scare off evil spirits.

But isn’t Halloween a Christian thing?

Halloween themed cupcakes (Picture:Getty)

Halloween also marks the day before the feast of All Saints Day (also known as All Hallows), a day that dates back to the eighth century and was designed to stamp out pagan traditions and convert people to Christianity.

On this day, Christians would honour the saints and pray for spirits who hadn’t yet reached heaven.

Why do we go trick or treating?

Rear view of three children wearing halloween costumes (Picture:Getty)

Trick or treating started in Ireland, Scotland and Wales and involved people dressing up in costumes and knocking on doors asking for food. The groups would offer up poems and songs in exchange for the food.

This trick or treat tradition evolved into children exchanging prayers for the dead in exchange for ‘soul cakes’ in the 11th century in a tradition called ‘souling’. These soul cakes were sweet with a cross on the top and they were intended to represent a spirit being freed from purgatory when eaten.

By the 19th century, this had evolved into a tradition where children would sing songs, tells jokes and read poems instead of prayers for pieces of fruit and money. Later, the children would play threatening pranks on people to get them to hand over sweets.

The name ‘trick or treat’ was first used in America in 1929 after immigrants took traditions surrounding the day overseas.

Why do we dress up?

Woman with blood around her mouth and glowing eyes (Picture:Getty)

People first started dressing up as souls of the dead, angels and saints for Halloween hundreds of years ago.

The origins of doing this – particularly among the trick or treaters – was because people believed impersonating the spirits in this way would offer protection from them.

Why do we carve pumpkins?

Halloween pumpkin (Picture: Alamy)

This goes back to the Samhain festival when people would decorate their homes to ward off bad spirits. They used to carve turnips and over time this evolved into carving pumpkins. This is believed to be because when Irish immigrants were in America they could only find pumpkins to carve. The pumpkin carving tradition took off properly in the 1920s.

The term ‘Jack O’Lantern’ is believed to have come from the folk story of Stingy Jack who tricked the devil into buying him a drink. Because of this, when he died he wasn’t allowed into heaven or hell but instead was trapped by the devil instead a burning ember, which was kept inside a turnip.